Armored forces loyal to Syrian President Bashar Assad moved into the rebel district of Baba Amro in Homs on Thursday after 20 days of sustained bombardment, opposition sources said.
Homs-based activist Abu Imad said tanks had entered the Jobar area in the south of Baba Amr.
"Explosions are shaking the whole of Homs. God have mercy," Abdallah al-Hadi said from the city, where more than 80 people, including two Western journalists and Syrian opposition citizen journalist Rami al-Sayed, were reported killed on Wednesday.
Meanwhile, opposition activists reported that at least 14 people have been killed by Syrian government troops in a crackdown on a village near Deir al-Zour, the largest city in the country's north-eastern part.
Two children are believed to be among the victims of the raid by soldiers backed by tanks on the village of al-Khoreita.
Earlier this week activists said that Syrian military sent columns of tanks and other reinforcements toward Homs.
A flood of military reinforcements has been a prelude to previous offensives by the authoritarian regime, which has tried to use its overwhelming firepower to crush an opposition that has been bolstered by defecting soldiers and hardened by 11 months of street battles.
"Most of the deaths occurred in the province of Homs. Others were killed in the provinces of Idlib and Hama," Omar Idlibi, the LCC spokesman in Beirut, told dpa.
Also on Thursday, a panel of United Nations experts drew up a list of Syrian officials who could be charged with crime against humanity, including Assad himself.
According to the report Syrian forces have shot dead unarmed women and children, shelled residential areas and tortured wounded protesters in hospital under orders from the "highest level" of army and government officials.
Syria on Thursday denied deliberately targeting two Western journalists killed in shelling attacks in the city of Homs, state-run television said.
"We reject statements holding Syria responsible for the death of the two journalists who had sneaked into the country at their own risk," the broadcaster said, quoting a statement from the Foreign Ministry.
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